PROJECT SUMMARY The HIV epidemic continues to disproportionately impact men who have sex with men (MSM) and African American populations in the United States (US). Pre-exposure prophylaxis (PrEP) has demonstrated efficacy in preventing HIV acquisition among at-risk populations. Despite high efficacy, PrEP implementation across the US has been slow, and approaches to evaluate implementation and determine gaps in coverage have been limited. The goal of this study is to evaluate and inform PrEP implementation efforts with a novel ?big data? approach using the Rhode Island All Payers Claims Database (APCD). APCDs are an emerging data source that contain insurance claims from Medicaid, Medicare, and most, if not all, private insurers. Rhode Island is one of the first states in the country to adopt an APCD. This study will develop and validate an algorithm to measure PrEP uptake and persistence using the RI APCD (Aim 1), describe PrEP implementation across the state including which physicians are prescribing PrEP and characteristics of the patients PrEP is being prescribed to (Aim 2), and assess the impact of insurance cost-sharing (e.g. co-pays, deductibles, and co-insurance) on PrEP uptake and persistence (Aim 3). Results of this study will provide the groundwork for the development of structural-level interventions to promote PrEP uptake among high-risk populations and inform state and federal policies pertaining to PrEP implementation.